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Reduce diff for attestation production
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@paulhauner
paulhauner committed Jun 28, 2022
1 parent 2afe98d commit f3ac736
Showing 1 changed file with 78 additions and 73 deletions.
151 changes: 78 additions & 73 deletions beacon_node/beacon_chain/src/beacon_chain.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1431,89 +1431,94 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
* the head-lock is not desirable.
*/

let head_state_slot;
let beacon_block_root;
let beacon_state_root;
let target;
let current_epoch_attesting_info: Option<(Checkpoint, usize)>;
let attester_cache_key;
let head_timer = metrics::start_timer(&metrics::ATTESTATION_PRODUCTION_HEAD_SCRAPE_SECONDS);
let cached_head = self.canonical_head.cached_head();
let head = &cached_head.snapshot;
let head_state = &head.beacon_state;
let head_state_slot = head_state.slot();

// There is no value in producing an attestation to a block that is pre-finalization and
// it is likely to cause expensive and pointless reads to the freezer database. Exit
// early if this is the case.
let finalized_slot = head_state
.finalized_checkpoint()
.epoch
.start_slot(slots_per_epoch);
if request_slot < finalized_slot {
return Err(Error::AttestingToFinalizedSlot {
finalized_slot,
request_slot,
});
}
// The following braces are to prevent the `cached_head` Arc from being held for longer than
// required. It also helps reduce the diff for a very large PR (#3244).
{
let head = self.head_snapshot();
let head_state = &head.beacon_state;
head_state_slot = head_state.slot();

// There is no value in producing an attestation to a block that is pre-finalization and
// it is likely to cause expensive and pointless reads to the freezer database. Exit
// early if this is the case.
let finalized_slot = head_state
.finalized_checkpoint()
.epoch
.start_slot(slots_per_epoch);
if request_slot < finalized_slot {
return Err(Error::AttestingToFinalizedSlot {
finalized_slot,
request_slot,
});
}

// This function will eventually fail when trying to access a slot which is
// out-of-bounds of `state.block_roots`. This explicit error is intended to provide a
// clearer message to the user than an ambiguous `SlotOutOfBounds` error.
let slots_per_historical_root = T::EthSpec::slots_per_historical_root() as u64;
let lowest_permissible_slot = head_state.slot().saturating_sub(slots_per_historical_root);
if request_slot < lowest_permissible_slot {
return Err(Error::AttestingToAncientSlot {
lowest_permissible_slot,
request_slot,
});
}
// This function will eventually fail when trying to access a slot which is
// out-of-bounds of `state.block_roots`. This explicit error is intended to provide a
// clearer message to the user than an ambiguous `SlotOutOfBounds` error.
let slots_per_historical_root = T::EthSpec::slots_per_historical_root() as u64;
let lowest_permissible_slot =
head_state.slot().saturating_sub(slots_per_historical_root);
if request_slot < lowest_permissible_slot {
return Err(Error::AttestingToAncientSlot {
lowest_permissible_slot,
request_slot,
});
}

if request_slot >= head_state.slot() {
// When attesting to the head slot or later, always use the head of the chain.
beacon_block_root = head.beacon_block_root;
beacon_state_root = head.beacon_state_root();
} else {
// Permit attesting to slots *prior* to the current head. This is desirable when
// the VC and BN are out-of-sync due to time issues or overloading.
beacon_block_root = *head_state.get_block_root(request_slot)?;
beacon_state_root = *head_state.get_state_root(request_slot)?;
};
if request_slot >= head_state.slot() {
// When attesting to the head slot or later, always use the head of the chain.
beacon_block_root = head.beacon_block_root;
beacon_state_root = head.beacon_state_root();
} else {
// Permit attesting to slots *prior* to the current head. This is desirable when
// the VC and BN are out-of-sync due to time issues or overloading.
beacon_block_root = *head_state.get_block_root(request_slot)?;
beacon_state_root = *head_state.get_state_root(request_slot)?;
};

let target_slot = request_epoch.start_slot(T::EthSpec::slots_per_epoch());
let target_root = if head_state.slot() <= target_slot {
// If the state is earlier than the target slot then the target *must* be the head
// block root.
beacon_block_root
} else {
*head_state.get_block_root(target_slot)?
};
let target = Checkpoint {
epoch: request_epoch,
root: target_root,
};
let target_slot = request_epoch.start_slot(T::EthSpec::slots_per_epoch());
let target_root = if head_state.slot() <= target_slot {
// If the state is earlier than the target slot then the target *must* be the head
// block root.
beacon_block_root
} else {
*head_state.get_block_root(target_slot)?
};
target = Checkpoint {
epoch: request_epoch,
root: target_root,
};

let current_epoch_attesting_info = if head_state.current_epoch() == request_epoch {
// When the head state is in the same epoch as the request, all the information
// required to attest is available on the head state.
Some((
head_state.current_justified_checkpoint(),
head_state
.get_beacon_committee(request_slot, request_index)?
.committee
.len(),
))
} else {
// If the head state is in a *different* epoch to the request, more work is required
// to determine the justified checkpoint and committee length.
None
};
current_epoch_attesting_info = if head_state.current_epoch() == request_epoch {
// When the head state is in the same epoch as the request, all the information
// required to attest is available on the head state.
Some((
head_state.current_justified_checkpoint(),
head_state
.get_beacon_committee(request_slot, request_index)?
.committee
.len(),
))
} else {
// If the head state is in a *different* epoch to the request, more work is required
// to determine the justified checkpoint and committee length.
None
};

// Determine the key for `self.attester_cache`, in case it is required later in this
// routine.
let attester_cache_key =
AttesterCacheKey::new(request_epoch, head_state, beacon_block_root)?;
// Determine the key for `self.attester_cache`, in case it is required later in this
// routine.
attester_cache_key =
AttesterCacheKey::new(request_epoch, head_state, beacon_block_root)?;
}
drop(head_timer);

// Drop the `Arc` to avoid keeping the reference alive any longer than required.
drop(cached_head);

// Only attest to a block if it is fully verified (i.e. not optimistic or invalid).
match self
.canonical_head
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